The cogeneration is the combination of power (energy) and heat. Here in this technical paper the power production without harming t h e environment is discussed. Nowadays electricity is in demand. In order to full fill this we can get the electricity by means of fossil fuels, and we can also generate heat, emission of carbon dioxide is reduced. Cost Efficiency is low. It also talks about benefits application efficiency and cogeneration technology. In this paper mainly about the fossil fuel (coal) has been discussed very widely.